I have posted some simulations of an overdamped geophone.  The phone is
modeled after a Vinci VT32 - a typical 10Hz geophone.

The simulations are posted here:

  http://www.c-c-i.com/2.3412358971118/

The simulations cover responses with the following values of damping:

	damping		load resistor
=====================================
..316	natural		open circuit
..7	critical	1000 ohms
1.	over		391 ohms
2.	over		-75.9 ohms
5.	over		-280 ohms
10.	over		-339 ohms
20.	over		-368 ohms
50.	over		-382 ohms
100.	over		-390 ohms

For each value of damping there are four plots - the frequency and step
responses at the phone output and the frequency and step responses at
the output of an ideal integrator (tau = 1 second) that corrects the
Lippmann response back to velocity.

The plots are listed in order of the above damping sequence on the web
page.

The simulations are built with ideal elements.  I am working on, and
will post, simulations using op-amp models which will include noise
calculations for the circuits.

Best regards,

==================================================================
Bob Smither                                        Bob@...........

  "We make money the old fashioned way.  We print it."
   --Art Rolnick, Chief Economist, Minnepolis Federal Reserve Bank
==================================================================

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